Drilling equipment for boring into subsurface formations is used in a variety of industrial applications. One particular application is in seismic drilling, which is commonly used in exploration for oil and gas. In seismic drilling, an explosive charge is detonated inside a borehole, and the resultant wave patterns generated in the soil structure in the vicinity of the borehole are recorded (or “logged”) using special electronic equipment. The seismic logs are interpreted by specialists to identify subsurface zones where crude oil or natural gas may be present.
It is generally desirable for seismic drills to be self-propelled so that they can easily moved from one borehole site to another without need for separate means of transport. It is also desirable for seismic drills to be adapted for operation on uneven ground surfaces, particularly when used in hilly or mountainous areas. It is further desirable for seismic drills to be comparatively small in physical size so that they will be more easily maneuverable over rough terrain and in forested areas. It is further desirable for seismic drills to be remotely controllable, to eliminate the need for a riding operator who would be exposed to the risk of injury in the event of the drill overturning or other mishaps which are particularly more likely to occur when operating in rough terrain.
Seismic drilling operations are commonly carried out in remote areas that are not accessible by roads, thus preventing the use of large truck-mounted seismic drilling equipment. It is well known, in such situations, to use drilling rigs that can be flown to the drilling site by helicopter (and therefore may be referred to as “heli-transportable” drills). The cost of transporting equipment by helicopter increases with the weight of the equipment and the size or type of helicopter being used. Accordingly, it is desirable to keep the weight of heli-transportable drilling equipment as low as possible in order for heli-transport to be economically feasible.
The ideal seismic rig for use in remote locations and rough terrain would incorporate all of the foregoing features, while still having the ability to drill seismic boreholes efficiently and to considerable depths.
Many of these desirable features can be individually found in the prior art. Examples of heli-transportable drills may be seen in U.S. Pat. No. 3,767,329 (Houck), U.S. Pat No. 3,981,485 (Eddy), U.S. Pat No. 4,192,393 (Womack), and U.S. Pat No. 4,476,940 (Reichert). However, none of these drills are self-propelled. The Houck drill is demountable for heli-transport, but its components weigh as much as 4,000 pounds, necessitating the use of a comparatively large helicopter and entailing correspondingly high helicopter operating costs.
Self-propelled drill rigs are well known, as are rigs that are articulated and/or track-mounted to facilitate travel over rough terrain. For example, U.S. Pat. No. 3,744,574 (Carley) discloses an articulated, self-propelled, wheel-mounted rock drill. U.S. Pat. No. 6,152,244 (Rokbi) discloses an articulated wheel-mounted drill. Examples of prior art track-mounted drills include U.S. Pat. No. 3,289,779 (Feucht) and U.S. Pat. No. 3,478,832 (Hughes). Each of the foregoing prior art drills is comparatively large and heavy, and neither adapted nor readily adaptable for transport by helicopter.
What is needed, therefore, is a self-propelled seismic drill that is adapted for efficient operation over rough or uneven terrain, and that can be transported by smaller helicopters than known heli-transportable drills. The present invention is directed to these needs.